1. Field of the Invention
This invention relates to an air/fuel ratio control apparatus for a general-purpose internal combustion engine, particularly to an air/fuel ratio control apparatus for a general-purpose engine using mixed fuel containing alcohol and gasoline.
2. Description of the Related Art
Conventionally, there is proposed a technique for an engine using mixed fuel containing alcohol and gasoline, which is configured to provide an air/fuel ratio sensor (O2 sensor (oxygen sensor) or a wide-range air/fuel ratio sensor in the exhaust system to detect an air/fuel ratio to determine a deviation from a predetermined value caused due to the mixed alcohol, estimate a rate of the alcohol in the fuel based on the detected deviation of the air/fuel ratio, and determine a fuel injection amount based on one from among sets of characteristics (maps or mapped data) selected from the estimated alcohol rate (or correct the fuel injection amount by the estimated alcohol rate), thereby controlling a fuel injection amount, as taught, for example, in Japanese Laid-Open Patent Application No. Sho 63 (1988)-5131.